German Chancellor Angela Merkel stressed the importance of freedom of opinion in talks with Turkish President Tayyip Erdogan on Thursday, during a visit meant to help improve frayed ties between the two NATO allies.

According to Reuters news agency, Merkel said she had agreed with Erdogan on the need for closer cooperation in the fight against terrorism,including the Kurdistan Workers Party (PKK).

Germany and Turkey have been at odds over Ankara’s crackdown on dissidents since the abortive July 15 coup, as well as its allegations – rejected by Berlin – that Germany is harbouring Kurdish and far-leftist militants.

“With the (attempted) putsch, we saw how the Turkish people stood up for democracy and for the rules of democracy,” Merkel told a news conference, when asked about concern over proposed constitutional changes that would strengthen Erdogan’s powers.

“In such a time of profound political upheaval, everything must be done to continue to protect the separation of powers and above all freedom of opinion and the diversity of society,” she said, adding she had also raised the issue of press freedom.

“Opposition is part of democracy,” Merkel said. Turkey’s allies, including Germany, fear Erdogan is using the coup attempt as a pretext to curtail dissent and Erdogan’s opponents fear the planned constitutional changes will lead to an authoritarian state.

The constitutional reform bill was submitted to Erdogan later on Thursday, parliamentary sources said. Once he approves it, the electoral commission will set a date for a referendum, expected in April.

“It is out of the question for the separation of powers to be abolished,” Erdogan said of the proposals, which would replace Turkey’s parliamentary system with an executive presidency.

“It gives more opportunity for the executive branch to work more swiftly. The judiciary will retain its power and function as usual with the new system.”